Cathode ray tube



Dec. 13, 193%. M. KNOLL CATHODE RAY TUBE Filed Aug. 4, 1954 INVENTOR.

MAX N0 L BY ATTORNEY Patented Dec. 13, 1938 2,139,829

UNITED STATES PATENT OFFlCE CATHODE RAY TUBE Max Knoll, Berlin, Germany, assignor to Telei'unken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application August 4, 1934, Serial No. 738,433 In Germany August 2, 1933 1 Claim. (Cl. 250-462) This invention relates to cathode ray tubes and provision of the diaphragm l2 the influence of more particularly, to method and means of shieldthe said field upon the speed of the cathode ray ing deflecting electrode structures provided withpencil, as a matter of fact, is lessened. in such tubes. Another means to eliminate the said lack of The invention is predicated upon this consharpness consists in that protective electrodes sideration and fact that in Braun tubes having a are disposed in the vicinity of the deflector plates, fluorescent screen having a diameter that is comfor example, in a way as shown in Fig. 2. These paratively large compared with the length of the protective electrodes 84 are at an invariable and deflected cathode ray pencil as required for telelower potential in reference to the tube wall vision reception, the electrical fields which are than the deflector plates, preferably at the very 10 set up between pairs of deflector plates thempotential of the tube walls.

selves or between one deflecting plate and the The said drawbacks of the earlier Braun tubes metallic layer coating the tube wall, occasion an will also be reduced by that the deflector plates acceleration of the cathode rays which has a a e pr sed W h s a constant biasing p diiierent value for each point of the picture. The tential that, at maximum deflector potential, one

15 consequence is that the spot will not appear to plate is made about as p si iv as the Ot er On be of constant size for all points or places upon is negative in reference to the tube wall. The the screen usually disposed at right angles to same thing is attainable if the source of the dethe tube axis. I flector voltage is conductively connected in its To preclude this drawback, the deflector plates electrical midpoint with the wall of the tube. 20 and/or the screen according to this invention In Co j W t e mea s disclosed, or should be arranged in a way as hereinafter to be ls ind p nd n y r h Said ffec of the described. The said difflculty can be avoided lac of s a p e s y be avoided y that e also by the circuit arrangement of the deflector surface of the fluorescent screen is inclined in plates. reference to the plane at right angles to the tube 25 In the drawing Figure 1 shows plan and elevaaxis. This inclination should be chosen in such tion Views of an electrode system embodying my a way that the particular corner of the screen invention. Fig. 2 shows a plan and elevation which the cathode ray pencil reaches if the maxiview of a modification of the embodiment shown mum deflection voltage is applied to the two pairs 0 in Figure 1. of deflecting plates, will be at the greatest dis- Referring to Figs. 1 and 2 the deflector plate tance.

pairs are designated by Ill and H. Between these Having thus described the invention, What I is mounted a diaphragm i2 having an oblong claim is: aperture l2 which is in conductive connection A cathode ray tube comprising an envelope, a

W W t t e m ic l g B3 of the tube. The conductive coating upon the inner wall of said force lines of the electrical field which, in the abenvelope, deflecting electrodes withi said sence of the diaphragm i2 Wallld e, O t e velope, cylindrical shield electrodes lying adjaone d. between the d t plate pair in cent to and in the same plane as the deflecting and the plate pair H, on the other hand, in an electrodes, and electrically conductive connecarrangement a wn in Fig. l, terminate on tions between said shield electrodes and the con- 40 the diaphragm 12 so that only a minor portion ductive coating. thereof will traverse through the space passed by MAX KNOLL. the cathode ray pencil. In other words, by the 

